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P0420 Catalyst System Efficiency Below Threshold

DTC P0420: Catalyst System Efficiency Below Threshold
NOTE:

  • Before you troubleshoot, review the general troubleshooting information.
  • If some of the DTCs listed below are stored at the same time as DTC P0420, troubleshoot them first, then recheck for DTC P0420.
    P0137, P0138: Secondary HO2S (Sensor 2)
    P0141: Secondary HO2S (Sensor 2) heater
    P0300: Random misfire
    P0301, P0302, P0303, P0304: No. 1-No. 4 cylinder misfire
  • Poor quality fuel may cause this DTC

DTC Troubleshooting: P0420 7015

  1. Do the diluted oil regeneration procedure. (E85)
  2. Do the fuel alcohol content learning. (E85)
  3. Turn the vehicle to the ON mode.
  4. Clear the DTC with the HDS.
    Clear DTC
  5. Start the engine.
  6. Hold the engine speed at 3,000 min-1 (rpm) without load (CVT in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.
  7. Test-drive the vehicle under these conditions:
    Engine coolant temperature (ECT SENSOR 1) above 70 °C (158 °F)
    CVT in D, M/T in 4th or 5th
    Vehicle speed between 70-120 km/h (45-75 mph) for 5 minutes or more with cruise control set
    Vehicle speed between 90-120 km/h (55-75 mph) for 10 seconds, then decelerate (with the throttle fully closed). Repeat this three or more times
    Maintain the vehicle speed at 90 km/h (55 mph) for 4 minutes or more with cruise control set.
  8. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the HDS.

Does the HDS indicate FAILED?

YES
Replace the TWC (three way catalytic converter).

NO
If the HDS indicates EXECUTING, go to step 2. If the HDS indicates OUT OF CONDITION, meet the test conditions and recheck. If the on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the on-board snapshot. If the HDS indicates PASSED, intermittent failure the system is OK at this time.

  1. Continue test-drive until a result comes on.
  2. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the HDS.

Does the HDS indicate FAILED?

YES
Replace the TWC (three way catalytic converter).

NO
If the HDS indicates PASSED, intermittent failure, the system is OK at this time. If the on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the on-board snapshot. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, meet the test conditions and recheck.

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